Simple Java TCP socket protocols

Question

I'm trying to find a reliable way to send control messages that obey a defined protocol in order to tell the server what kind of data he will receive. For example, I want to send a pure text message to invoke a remote method:

#METHOD1#CLOSE#

or I want to send a serialized object to the server:

#OBJECT# .......here comes the serialized object data....#CLOSE#

So basically I just want to send string control messages that are completely independent of the stream content that follows.

By wrapping an input stream into a Scanner object I'm able to extract strings from the input stream, but if this stream is a serialized object then the object can't be restored afterwards. Thanks for any help.

Why don't you just use one of the many existing protocols for this purpose? For instance, JSON-RPC? Do you have any specific requirements? — fge
– fge, Commented May 27, 2013 at 16:14
If possible, it should be a pure socket based solution. I just would like to know how this could be done. — user1812379
– user1812379, Commented May 27, 2013 at 16:27
"if possible" is no valid reason. Which is why I asked for your requirements. There is no reason at all to hack your own protocol if an existing one already fits your need. Do not reinvent the wheel! — fge
– fge, Commented May 27, 2013 at 16:58
It's an assignment. Protocols for strings are not a problem, because I can easily append a control message to the actual message string. However, the easierst solution seems to be to subclass ObjectOutputStream. — user1812379
– user1812379, Commented May 27, 2013 at 18:59

Radiance Ong · Accepted Answer · 2013-05-27 16:36:31Z

1

You can use a scheme like Base64 (e.g. use a library from Apache) to encode the Object from bytes into a string and then back.

ByteArrayOutputStream baos = new ByteArrayOutputStream();
new ObjectOutputStream(baos).writeObject(object);
String serializedObject = Base64.encode(baos.toByteArray());

byte[] bytes = Base64.decode(serializedObject);
ByteArrayInputStream baos = new ByteArrayInputStream(bytes);
Object object = new ObjectInputStream(baos).readObject()

answered May 27, 2013 at 16:36

Radiance Ong

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2 Comments

user1812379 Over a year ago

What about Java's BASE64Encoder/Decoder? So, basically I have to encode the object to a string and then append that object string to the control message string, right? To decode the message I read the chars that represent the control message and, if the message says it's an object, I go on adn decode the rest of the string to an object.

Radiance Ong Over a year ago

Yes, that's right. You can use any Base64 encoder/decoder you like.

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